Note: This column is for information purposes only and is not intended as a substitute for professional medical advice.

Q: There has been much publicity regarding deep vein thrombosis and economy-class plane travel. Do you know of any research linking DVT, flying and polio survivors?

A: The brief sturm und drang about DVT in transoceanic airline passengers may end up being just another example of "media medicine." If DVT were so common, with the hundreds of thousands of air travelers jetting all around the globe on six to sometimes 24-hour flights, hospitals would have to be built at the end of runways to handle all the new clotted patients.

Compare flying as a cause of DVT to some polio survivors' lives. There are individuals who have not moved their legs in 50 years-- somewhat longer than the six-hour flight from New York to London-- and have never had a DVT. In 20 years we have seen no higher incidence of DVT in polio survivors than in the general population, despite polio survivors not moving their leg muscles for years, which should make DVT more likely-- if it's true that a plane trip does.

Some polio survivors' doctors do worry about cold and purple "polio feet," which are caused by blood pooling in the veins near the surface of the skin. This happens because the nerves that contract the muscle around the veins have been killed off by the poliovirus (see PPS Forum, March 2001). But there is no evidence that blood pools in polio survivors' deep muscle veins where DVT forms. However, if your calves are painful or hot, you could have DVT and should see a doctor. Polio survivors aren't immune from DVT. And because many polio survivors have more swelling due to blood pooling in their legs as they age, you should keep your feet elevated whenever you can. Maybe the flap about DVT will get you a free medical upgrade to first class, where you can put your gams up and get a good meal.

Q: Is there a connection between Lou Gehrig's disease (ALS--amyotrophic lateral sclerosis), polio and PPS? I know both are neurological diseases. My mother died from ALS in her 40s. My sister-in-law's mother had polio when she was 39 and was married to a man who eventually got ALS. Could exposure to polio or polio survivors be connected to ALS?

Fortunately, PPS isn't a disease. It's a wearing out of poliovirus-damaged, overworked motor neurons and overused joints and muscles. But a possible connection between ALS and polio is how we found out about PPS.

Twenty years ago I happened to take a phone call from a 36-year-old polio survivor. He had developed weakness in one arm and had been given a death sentence. Weakness on one side of the body is a symptom of ALS, the fatal neurological disease causing progressive paralysis of muscles throughout the body due to motor neurons dying. His neurologist said, because of the weakness in one arm, that he must have "some kind of ALS" and that he was going to die. But something was very wrong with that diagnosis. The man only had one arm that could become weaker, since the other arm had been completely paralyzed by polio when he was a child. Testing quickly revealed that he did not have ALS. He had what would one day be called post-polio sequelae.

The notion that new weakness in polio survivors might be ALS was first raised in 1903. American doctor Charles Potts wrote the 20th century's first article on "the late effects" of polio. He reviewed the nearly three dozen cases of new muscle weakness in polio survivors that had been published since a French polio survivor's fatigue and weakness was first reported in 1875. Potts thought that two of those polio survivors did have ALS, but that the rest did not.

In 1962 K.J. Zilkha was the first to follow the course of muscle weakness in polio survivors over many years. He reported that, although polio survivors could become weaker with time, they did not develop an inability to swallow and breathe, the life-threatening muscle paralysis characteristic of ALS. A dozen studies since then have shown that there is no relationship between PPS and ALS, nor does exposure to polio survivors cause ALS. Under no circumstances are polio survivors--with or without PPS--contagious in any way, since they stopped shedding virus about 10 days after the polio attack.